Light emitting device

ABSTRACT

A light emitting device ( 100 ) according to the present disclosure includes a base substrate ( 10 ) having a recessed portion ( 15 ) at its upper surface ( 11 ); a light emitting element ( 20 ) provided in the recessed portion ( 15 ); and a sealing member ( 30 ) provided in the recessed portion ( 15 ), in which the sealing member ( 30 ) contains surface-treated particles ( 40 ), or particles ( 40 ) coexisting with a dispersing agent, and at least a part of an edge portion of the sealing member ( 30 ) is a region located in the vicinity of an edge ( 17 ) of the recessed portion, and in which at least one of the particles ( 40 ) and aggregates ( 41 ) of particles are unevenly distributed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority based on Japanese Patent ApplicationNo. 2013-251586 filed on Dec. 5, 2013 in Japan, which is incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The disclosure relates to a light emitting device including a lightemitting element, and a sealing member for sealing the light emittingelement.

2. Description of the Related Art

Conventionally, some light emitting devices are manufactured bydisposing a light emitting element in a recessed portion of a package,connecting the light emitting element to a lead frame via wires, fillinga sealing resin into the recessed portion, and then curing the resin(see, for example, JP 2010-080620 A and JP 2011-222718 A).

In such a light emitting device, however, the sealing resin unexpectedlyleaks and spreads from the recessed portion of the package onto theupper surface thereof due to high wettability of a liquid base materialof the sealing resin.

SUMMARY OF THE INVENTION

The present invention has been made in view of the foregoingcircumstances, and it is an object of embodiments of the presentinvention to provide a light emitting device that can suppress theleakage and spread of a sealing member from a recessed portion of a basesubstrate onto an upper surface thereof.

In order to solve the foregoing problems, a light emitting deviceaccording to one embodiment of the present invention includes: a basesubstrate having a recessed portion at its upper surface; a lightemitting element provided in the recessed portion; and a sealing memberprovided in the recessed portion, wherein the sealing member containssurface-treated particles, or particles coexisting with a dispersingagent, and at least a part of an edge portion of the sealing member is aregion located in the vicinity of an edge of the recessed portion, andin which at least one of the particles and aggregates of particles areunevenly distributed.

Accordingly, embodiments of the present invention can suppress theleakage and spread of the sealing member onto the upper surface of thebase substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic top view of a light emitting device according toone embodiment of the present invention; FIG. 1B is a schematiccross-sectional view taken along the line A-A of FIG. 1A.

FIGS. 2A and 2B are schematic diagrams for explaining the principle ofsuppressing the leakage and spread of a sealing member in the embodimentof the present invention.

FIG. 3 is a graph showing the relationship between the content ofsurface-treated particles of the sealing member, and the leakage andspread of the sealing member onto the upper surface of the basesubstrate in the light emitting device in the one embodiment of thepresent invention.

FIG. 4A is a schematic top view of a light emitting device according toanother embodiment of the present invention; FIG. 4B is a schematiccross-sectional view taken along the line B-B of FIG. 4A.

FIG. 5 shows images of the top surface of an edge portion of the sealingmember in the light emitting device observed by a scanning electronmicroscope in one Example of the present invention.

FIG. 6 is data on the result of an energy dispersive X-ray analysis ofthe edge portion of the sealing member shown in FIG. 5.

FIG. 7 shows an image of a section of the edge portion of the sealingmember shown in FIG. 5 and observed by the scanning electron microscope.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention will be described belowwith reference to the accompanying drawings as appropriate. Note that alight emitting device to be mentioned later is intended to embody thetechnical concept of the present invention, and not to restrict thescope of the present invention to the following embodiments unlessotherwise specified. The contents of one embodiment and one Example ofthe present invention mentioned below can also be applied to otherembodiments and Examples. In some drawings, the sizes or positionalrelationships of members are emphasized to clarify the descriptionbelow.

First Embodiment

FIG. 1A shows a schematic top view of a light emitting device accordingto a first embodiment of the present invention, and FIG. 1B is aschematic cross-sectional view taken along the line A-A of FIG. 1A.

As shown in FIGS. 1A and 1B, a light emitting device 100 in the firstembodiment includes a base substrate 10, a light emitting element 20 anda sealing member 30. The base substrate 10 has a recessed portion 15 atits upper surface 11. The light emitting element 20 is provided in therecessed portion 15. The sealing member 30 is also provided in therecessed portion 15.

More specifically, the light emitting device 100 is a surface mountingtype LED. The light emitting device 100 includes the base substrate 10with the recessed portion 15 formed at the upper surface 11, two lightemitting elements 20 accommodated in the recessed portion 15, and thesealing member 30 filled into the recessed portion 15 to cover all thelight emitting elements 20. The base substrate 10 is a package includingconductive members, and a molded body for holding the conductivemembers. The conductive members are a pair of positive and negative leadelectrodes. The molded body may be a white resin molded body. A part ofthe bottom surface of the recessed portion 15 of the base substrate isconstituted by the upper surfaces of the conductive members. Each of thetwo light emitting elements 20 may be a LED element, bonded to thebottom surface of the recessed portion 15 of the base substrate by anadhesive, and connected to the conductive members via the wires. Thesealing member 30 includes resin as a base material 35. The sealingmember 30 may contain phosphors 50. The phosphors 50 are unevenlydistributed on the bottom side of the recessed portion 15.

The sealing member 30 contains particles 40 surface-treated. At least apart of the edge portion of the sealing member 30 is a region located inthe vicinity of an edge 17 of the recessed portion, and in which atleast one of the particles 40 and aggregates 41 of the particles 40 areunevenly distributed.

Thus, the light emitting device 100 with this arrangement can suppressthe leakage and spread of the sealing member 30 from the recessedportion 15 of the base substrate onto the upper surface 11 thereof dueto high wettability of a liquid base material of the sealing member.

The region of the sealing member 30 located in the vicinity of the edge17 of the recessed portion of the base substrate and in which at leastone of the particles 40 and aggregates 41 thereof are unevenlydistributed may be a part of the edge portion of the sealing member 30,but preferably occupies half or more the edge portion of the sealingmember 30 (for example, half or more the entire periphery of the edgepart), and more preferably occupies substantially the entire edgeportion of the sealing member 30 (for example, the substantially entirelength of the entire periphery of the edge part).

The edge (border) 17 of the recessed portion 15 of the base substrate asused in the present specification indicates a boundary between an innerwall surface of the recessed portion 15 of the base substrate and theupper surface 11. Further, the vicinity of the edge 17 of the recessedportion of the base substrate corresponds to the vicinity of theabove-mentioned boundary, and includes not only the inner wall surfaceside of the recessed portion 15 of the base substrate, but also theupper surface 11 side of the base substrate.

In this embodiment, the surface-treated particles 40 may be replaced byparticles that coexist with a dispersing agent (e.g. particles togetherwith a dispersing agent). In this case, the same function and effect canbe obtained. The particles coexisting with the dispersing agent areproduced by blending particles and the dispersing agent for dispersingthe particles into the sealing member, and as a result, for example,become particles with the dispersing agent adsorbed thereto.

Now, a description will be given of the principle that the leakage andspread of the sealing member 30 onto the upper surface 11 of the basesubstrate is suppressed by at least one of the particles 40 and theaggregates 41

FIGS. 2A and 2B are schematic diagrams for explaining the principle ofsuppressing the leakage and spread of the sealing member in theembodiment of the present invention. The principle of suppressing theleakage and spread of the sealing member includes two stages. A firststage will be described below with reference to FIG. 2A. In the firststage, the particles 40 that have little interaction therebetween, thatis, which have the cohesive property suppressed are dispersed into aliquid base material 35 of the sealing member, preferably, substantiallyuniformly dispersed thereinto. The material of the sealing member 30before solidification forms a meniscus end in the vicinity of the edge17 of the recessed portion when the material are put into the recessedportion 15 of the base substrate. A capillary force is generated betweenthe particle 40 existing at the tip of the meniscus end (near a contactpoint among three phases, namely, air (gas), a base material (liquid) ofthe sealing member, and a base substrate (solid)), and the particle 40existing at the tip of the adjacent meniscus end. The capillary forceworks to draw the particles 40 existing at the tips of the adjacentmeniscus ends close to each other. Then, the capillary forcecontinuously acts along the edge portion of the sealing member 30 (inthis embodiment, the edge 17 of the recessed portion of the basesubstrate), which can suppress the leakage and spread of the sealingmember 30 put into the recessed portion 15 of the base substrate beforeits solidification. In particular, the capillary force works along thesubstantially entire edge portion of the sealing member 30 (in thisembodiment, the substantially entire region of the edge 17 of therecessed portion of the base substrate), which can effectively suppressthe leakage and spread of the sealing member 30 before itssolidification. Note that the capillary force tends to be generated in acolloid solution having a high dispersibility of particles (see, forexample, B M. Weon, J H. Je, Self-Pinning by Colloids Confined at aContact Line, Phys. Rev. Lett. 110, 028303 (2013)). Thus, the capillaryforce can be effectively exhibited by applying a surface treatment tothe particles 40 for suppressing the agglomeration of the particles, orby blending the dispersing agent with the particles 40.

A second stage will be described below with reference to FIG. 2B. Thesecond stage involves heating for promoting the solidification of thesealing member 30. During the step of solidifying the sealing member 30,the above-mentioned meniscus end is very thin, so that a low-boilingpoint component of the base material 35 of the sealing member (forexample, a low-boiling point siloxane of a silicone resin) vaporizesmost quickly. A change in surface tension at the meniscus end due to thevaporization causes the flow of surface tension toward the meniscus endwithin the sealing member 30 before its solidification. Then, thesealing member 30 before its solidification delivered to the meniscusend is suppressed from leaking and spreading by the above capillaryforce to be returned inside the meniscus end. As a result, a convectiveflow is generated at the meniscus end. During this process, theparticles 40 delivered by the convective flow at the meniscus end arearranged in line by the capillary force, or are agglutinated due to alocal increase in concentration of the particles. In this way, theparticles 40 agglutinated at the edge portion of the sealing member 30further suppress the leakage and spread of the sealing member 30 whichhas its volume expanding by being heated and whose viscosity and surfacetension are decreased.

In the way mentioned above, at least a part of the edge portion of thesolidified sealing member 30 is a region in which at least one of theparticles 40 and aggregates 41 thereof are unevenly distributed. Sincethe capillary force depends on the dispersibility of the particles, thenumber of the particles 40 is preferably larger than that of theaggregates 41 of the particles from the viewpoint of suppressing theleakage and spread of the sealing member 30. However, the capillaryforce also acts on the aggregates 41 of the particles. The particles 40are agglutinated while the sealing member 30 is solidified. As a result,a relatively large number of the aggregates 41 of the particles areoften observed in the solidified sealing member 30.

The term “unevenly distributed” as used in the present specificationmeans the existence in a specific region in high density, but does notdeny the existence in low density in a region other than the specificregion. One preferred embodiment of the state of being “unevenlydistributed” means the existence in the specific region in high densitywith nothing existing in other regions.

Preferred embodiments of the light emitting device 100 will be describedbelow.

(Particle 40)

The particles 40 are blended into the base material 35 of the sealingmember, and have a function of suppressing the leakage and spread of thesealing member 30 onto the upper surface 11 of the base substrate. Theparticle 40 will be described in detail below. Note that when theparticles 40 are intended to be distinguished from a filler and aphosphor to be mentioned later for convenience in writing, hereinafter,the particle 40 is referred to as a first particle, and the filler andthe phosphor as other particles are referred to as a second particle anda third particle, respectively.

The particle 40 for use can have a particle diameter of, for example, 1nm or more and 100 μm or less, but are preferably a nanoparticle (whichcan be defined as a particle with a particle diameter of 1 nm or moreand 100 nm or less). The particles 40 which are nanoparticles can obtainthe capillary force even in a small amount, which can suppress theleakage and spread of the sealing member 30 onto the upper surface 11 ofthe base substrate. Especially, the particle 40 preferably has aparticle diameter of 5 nm or more and 50 nm or less. The aggregates 41of the particles are produced by agglutinating the particles 40. Theaggregates 41 of the particles are easily observed because of its largersize than the particle 40, so that the observation of the existence ofthe aggregate 41 can presume the existence of the particles 40. Thediameter of the aggregate 41 of the particles is, for example, in arange of about 100 nm to about 300 μm, and preferably 100 nm or more and100 μm or less. The particles 40 and the aggregate 41 thereof may havethe function of scattering the light from the light emitting element 20.In particular, when the particle 40 is a nanoparticle, ashort-wavelength light, such as blue ray, can be increasingly scatteredby Rayleigh scattering. The occurrence of the Rayleigh scattering easilyexcites the phosphor 50. Thus, the blending amount of the phosphor 50can be decreased to reduce the cost of the light emitting device.Further, a transmittance of the sealing member 30 can be improved toenhance the light extraction efficiency. Note that the particle diameterof the particle 40 can be defined by an average particle diameter (D₅₀).The diameter of the particle 40 or aggregate 41 can be measured by alaser diffusion-scattering method, an image analysis method (scanningelectron microscope (SEM), transmission electron microscope (TEM)), adynamic light scattering, an X-ray small angle scattering method, or thelike. More specifically, D₅₀ determined by observing a section using SEMor the like can be used as the diameter of the particle 40 or aggregate41.

The shape of the particle 40 is not specifically limited, and may havean irregular crushed shape or the like. However, the particle 40preferably has a spherical shape, and thus can minimize the contactbetween the particles to suppress the agglomeration of the particles.The particles 40 having a plate-like shape can impart a gas barrierproperty to the sealing member 30.

The particle 40 is not specifically limited, but may be an organicmaterial or inorganic material. The particle 40 is preferably made oftranslucent material in terms of the light extraction efficiency of thelight emitting device. The particle 40 preferably has a melting point of260° C. or higher from the viewpoint of resistance to heat forsoldering. Specifically, the organic materials preferably includepolymethacrylic acid ester and its copolymer, polyacrylic acid ester andits copolymer, a cross-linked polymethacrylic acid ester, a cross-linkedpolyacrylic acid ester, polystylene and its copolymer, a cross-linkedpolystyrene, an epoxy resin, a silicone resin, amorphous fluorine resin,and the like. The particle 40 may include a core-shell type particlethat is obtained by coating an inorganic particle with at least oneresin selected from the above materials. Such an organic particle canmatch its refractive index with that of the base material 35 of thesealing member by copolymerization. Even though the particles areagglutinated, the aggregates can maintain its translucency or the like,which has little influence on optical properties. On the other hand, theinorganic materials preferably include silicon oxide, aluminum oxide,zirconium oxide, titanium oxide, zinc oxide, magnesium oxide, galliumoxide, tantalum oxide, niobium oxide, bismuth oxide, yttrium oxide,iridium oxide, indium oxide, tin oxide, and the like. Such an inorganicparticle has excellent resistance to heat and light, and also has arelatively high thermal conductivity. Among them, silicon oxide,aluminum oxide, zirconium oxide, and titanium oxide are easilyavailable, and relatively inexpensive. In addition, the particle 40 foruse can be made of the same material as that of the phosphor 50 to bementioned later.

The particle 40 preferably undergoes the surface treatment (that is, anattached substance is formed on the surface of each particle 40 throughthe surface treatment). As a result, the agglomeration of the particles40 is suppressed, in other words, the dispersibility of the particles 40is improved, which can easily generate the above capillary force tosuppress the leakage and spread of the sealing member 30 onto the uppersurface 11 of the base substrate. The surface treatment on the particles40 is performed using, for example, long-chain aliphatic amine or aderivative thereof, long-chain aliphatic fatty acid or a derivativethereof, a silane coupling agent, a siloxane compound having an aminegroup and/or a carboxyl group, a siloxane compound having at least oneselected from the group consisting of a silanol group, a hydrogen silanegroup and an alcohol group, a siloxane compound having a vinylsilylgroup and at least one selected from the group consisting of a silanolgroup, an alkoxyl group and a hydrogen silane group, a siloxane compoundhaving a monoglycidyl ether endgroup, a siloxane compound having amonohydroxyl ether endgroup, an organic silazane compound, an organictitanate compound, an isocyanate compound, an epoxy compound, aphosphate compound, a phosphoester compound, and the like (that is, sucha derivative and/or a compound is attached to the surface of theparticle 40 by the surface treatment). The dispersing agents caninclude, in addition to the surface treatment material, a polymercompound having an acid group or a basic group, a fluorine-containedsurfactant agent, a polyol compound, a polyethylene oxide derivative, apolypropylene oxide derivative, a polyvalent fatty acid derivative, ahydrolysate of a silane coupling agent, a quaternary ammonium saltcompound, and the like. The particle 40 which is a nanoparticle ispreferably subjected to the surface treatment. On the other hand, theparticle 40 which is a micron particle is preferably blended with thedispersing agent.

FIG. 3 is a graph showing the relationship between the content ofsurface-treated particles of the sealing member and the leakage andspread of the sealing member onto the upper surface of the basesubstrate in the light emitting device 100 of the first embodiment. Arate of occurrence of the leakage and spread of the sealing member shownin FIG. 3 was determined through calculation by defining the leakage andspread of the sealing member leading to a cut position of an uppersurface of the base substrate 10 (to an angle formed by the uppersurface of the base substrate 10 and its end surface) in a singulatingstep of the light emitting device to be mentioned later as “occurrence”,and also defining the leakage and spread below this boundary as“non-occurrence”. As shown in FIG. 3, when the content of the particles40 and/or the aggregates 41 thereof is 0.05% by weight or more, theeffect of suppressing the leakage and spread of the sealing member 30onto the upper surface 11 of the base substrate can be easily obtained.The upper limit of the content of the particles 40 and/or the aggregates41 thereof is not specifically limited from the viewpoint of obtainingthe effect of suppressing the leakage and spread of the sealing member30. However, when the content of the particles 40 and/or the aggregates41 thereof exceeds 50% by weight, the excessive increase in viscosity orthe white turbidity of the sealing member 30, or the excessiveagglomeration of the particles 40 might be caused. Thus, the content ofthe particles 40 and/or the aggregates 41 thereof is preferably 0.05% byweight or more and 50% by weight or less. In particular, when thecontent of the particles 40 and/or the aggregates 41 thereof ispreferably 0.1% by weight or more and 20% by weight or more, the effectof suppressing the leakage and spread of the sealing member 30 onto theupper surface 11 of the base substrate is stably obtained, whileappropriately maintaining the properties of the sealing member 30. Thecontent of the particles 40 and/or the aggregates 41 thereof is morepreferably 0.2% by weight or more and 2.0% by weight or less, andfurther may be 0.2% by weight or more and less than 0.5% by weight .Note that the content of the particles 40 and/or the aggregates 41thereof corresponds to the amount of blending of the particles 40, andis represented in weight percent as a ratio with respect to the basematerial 35 of the sealing member. In this way, the blending of theparticles 40 in a small amount can suppress the leakage and spread ofthe sealing member 30 onto the upper surface 11 of the base substrate,which is a great advantage in manufacturing the light emitting device.

In the light emitting device 100, the end surface of the base substrate10 is a cut surface. When the sealing member unexpectedly leaks orspreads from the recessed portion of the base substrate onto the uppersurface, the upper surface of the sealing member cannot be easily formedin a convex shape expanding upward, which makes it difficult to enhancea luminous flux density, or which causes a failure of solder leakage dueto the leakage or spread of the sealing member onto the conductivemember. However, the most serious problem is failure caused in thesingulating process of the base substrate. Some light emitting devicesare manufactured by performing a series of processes with a plurality ofbase substrates connected together in the longitudinal and lateraldirections until the sealing step is finished, and then singulating theconnected substrates into separated pieces. In the singulating step ofthe light emitting device, when cutting the sealing member formed acrossthe upper surfaces of the adjacent base substrates by a dicer or thelike, burrs might be caused in a cut part of the sealing member. Suchburrs of the sealing member might worsen the appearance of the lightemitting device and light distribution, or might cause damages to thelight emitting devices during storing the light emitting devices inlarge numbers. In this way, the suppression of the leakage and spread ofthe sealing member onto the upper surface of the base substrate is veryadvantageous to the light emitting device manufactured accompanied bythe cutting process of the base substrate.

The silicone resin is a relatively soft resin, and is difficult to cutby the dicer or the like. If the silicone resin needs to be cut, thesingulating step of the light emitting devices would be complicated. Inparticular, the suppression of the leakage and spread of the sealingmember 30 onto the upper surface 11 of the base substrate is furtheradvantageous to the light emitting device in which the base material 35of the sealing member is made of silicone resin, modified siliconeresin, silicone modified resin or hybrid silicone resin.

Second Embodiment

FIG. 4A shows a schematic top view of a light emitting device accordingto a second embodiment of the present invention, and FIG. 4B is aschematic cross-sectional view taken along the line B-B of FIG. 4A.

As shown in FIGS. 4A and 4B, a light emitting device 200 in the secondembodiment includes the base substrate 10, the light emitting element20, and the sealing member 30. The base substrate 10 has a recessedportion 15 at its upper surface 11. The light emitting element 20 isprovided in the recessed portion 15. The sealing member 30 is alsoprovided in the recessed portion 15.

More specifically, the light emitting device 200 is a surface mountingtype LED. The light emitting device 200 includes the base substrate 10with the recessed portion 15 formed at the upper surface 11, one lightemitting element 20 accommodated in the recessed portion 15, and thesealing member 30 filled into the recessed portion 15 to cover the lightemitting element 20. The base substrate 10 is a package includingconductive members, and a molded body for holding the conductivemembers. The conductive members are a pair of positive and negative leadelectrodes. The molded body may be a white resin molded body. A part ofthe bottom surface of the recessed portion 15 of the base substrate isconstituted by the upper surfaces of the conductive members. The lightemitting element 20 may be a LED element, and is bonded to the bottomsurface of the recessed portion 15 of the base substrate with anadhesive and thus connected to the conductive members via wires. Thesealing member 30 includes resin as a base material 35. The sealingmember 30 may contain phosphors 50. The phosphors 50 are unevenlydistributed on the bottom side of the recessed portion 15.

The sealing member 30 contains particles 40 surface-treated. At least apart of the edge portion of the sealing member 30 is a region located inthe vicinity of the edge 17 of the recessed portion, and in which atleast one of the particles 40 and aggregates 41 thereof are unevenlydistributed.

The light emitting device 200 with such a structure can also suppressthe leakage and spread of the sealing member 30 from the recessedportion 15 of the base substrate onto the upper surface 11. Also in thisembodiment, the surface-treated particles 40 can have the same functionsand effects even by being replaced by particles coexisting with adispersing agent. The particles coexisting with the dispersing agent maybe produced by blending particles and the dispersing agent fordispersing the particles into the sealing member, and as a result becomeparticles with the dispersing agent adsorbed thereto.

In the light emitting device 200, at least one of the particles 40 andthe aggregates 41 thereof also exist at the outer edge portion of thesealing member 30, that is, in the vicinity located outside of the edgeportion of the sealing member 30. The particles 40 and/or the aggregates41 thereof existing at the outer edge portion of the sealing member 30can act to interrupt the sealing member 30 to thereby suppress theleakage and spread of the sealing member 30 onto the upper surface 11 ofthe base substrate.

In the light emitting device 200, the upper surface of the sealingmember 30 is formed in a convex shape extending upward. The sealingmember 30 is suppressed from leaking and spreading onto the uppersurface 11 of the base substrate due to the particles 40 and/or theaggregates 41 unevenly distributed at the edge portion of the sealingmember. Thus, the amount of the base material 35 tends to be increased,thereby easily shaping the upper surface of the sealing member extendingupward in the convex shape. As a result, the light emitting device withexcellent light extraction efficiency can be easily obtained.

In the light emitting device 200, an inorganic coating 60 may be formedover the upper surface 11 of the base substrate. The coating 60 is tosuppress the degradation of the conductive member due to outside air ormoisture. The coating 60 may be formed over at least the conductivemember in terms of function. Normally, after mounting the light emittingelement 20 inside the recessed portion 15 of the base substrate, thecoating 60 is formed across the substantially entire region of the uppersurface of the base substrate 10. The coating 60 is made of, forexample, aluminum oxide, silicone oxide, aluminum nitride, siliconnitride, or a mixture thereof. The thickness of the coating 60 ispreferably 1 nm or more and 50 nm or less, and more preferably 2 nm ormore and 25 nm or less. The formation method of the coating 60 may besputtering or the like, but preferably an atomic layer deposition (ALD)method that can form a film with a constant certain thickness with highaccuracy. In this way, the inorganic coating 60 has a relatively largesurface energy, and allows the sealing member 30 to easily leak orspread onto the upper surface 11 of the base substrate. Thus, thesuppression of the leakage and spread of the sealing member 30 onto theupper surface 11 of the base substrate is very advantageous to the lightemitting device in which the inorganic coating 60 is formed over theupper surface 11 of the base substrate.

The respective components of the light emitting device in theembodiments of the present invention will be described below.

(Base substrate 10)

The base substrate serves as a member for a case or base over which thelight emitting element is mounted. The base substrate may be mainlycomposed of the conductive member electrically connected to the lightemitting element, and a molded body for holding the conductive element.The base substrate may take the form of a package, a wiring substrateand the like. Specifically, the base substrate can be a resin moldedbody formed integrally with a lead frame by transfer molding, injectionmolding or the like, or a product formed by laminating ceramic greensheets with a conductive paste printed thereon, and then calcining them,and the like. The upper surface of the base substrate is preferablysubstantially flat, but maybe warped. The upper surface of the basesubstrate has a recessed portion formed therein. The recessed portionmay be formed by recessing a molded body itself. Alternatively, aframed-like protrusion may be additionally formed on the substantiallyflat upper surface of the molded body to thereby form the recessedportion inside an area surrounded by the protrusion. The recessedportion can have a rectangular shape, a rectangular shape with a roundededge, a circular shape, an ellipse shape, or the like as viewed from thetop side. The sidewall surface of the recessed portion is preferablyinclined (which can include the warped surface) such that the diameterof the recessed portion is enlarged upward from the bottom surfacethereof in order to easily release the molded body from the die and toeffectively extract the light from the light emitting element (in whichan inclination angle is, for example, in a range of 95° or more and 120°or less from the bottom surface of the recessed portion). The depth ofthe recessed portion is not specifically limited, but for example, 0.05mm or more and 2 mm or less, preferably 0.1 mm or more and 1 mm or less,and more preferably 0.25 mm or more and 0.5 mm or less.

(Conductive Member)

Materials suitable for use in the conductive member can be metalmaterial capable of exhibiting conductivity by being connected to thelight emitting element. Specifically, the conductive member can be alead electrode or wiring formed of gold, silver, copper, iron, aluminum,tungsten, cobalt, molybdenum, chrome, titanium, nickel, palladium, or analloy thereof, phosphor bronze, iron-contained copper, and the like. Theconductive member may have as its surface layer, a coating or lightreflective film made of silver, aluminum, rhodium, gold, copper, or analloy thereof. Among them, silver having excellent reflectivity ispreferable.

(Molded Body)

Materials for the molded body can include, as a base material,thermoplastic resins such as an alicyclic polyamide resin, asemi-aromatic polyamide resin, polyethylene terephthalate,polycyclohexane terephthalate, a liquid crystal polymer, a polycarbonateresin, syndiotactic polystyrene, polyphenylene ether, polyphenylenesulfide, a polyether sulfone resin, a polyether ketone resin, and apolyarylate resin; and thermosetting resins such as a polybismaleimidetriazine resin, an epoxy resin, a modified epoxy resin, a siliconeresin, a modified silicone resin, a polyimide resin, and a polyurethaneresin. Into the base material, a filler or coloring pigment can beblended. The fillers or coloring pigments can include particles or fibermade of glass, silica, titanium oxide, magnesium oxide, magnesiumcarbonate, magnesium hydroxide, calcium carbonate, calcium hydroxide,calcium silicate, magnesium silicate, wollastonite, mica, zinc oxide,barium titanate, potassium titanate, aluminum borate, aluminum oxide,zinc oxide, silicon carbide, antimony oxide, zinc stannate, zinc borate,iron oxide, chrome oxide, manganese oxide, carbon black, and the like.Additionally, the molded body can also be formed of ceramics containingaluminum oxide, aluminum nitride, or a mixture thereof. Such ceramic hasnormally a larger surface energy than the above resin material, and thusallows the sealing member to easily leak and spread onto the uppersurface of the base substrate.

(Light Emitting Element 20)

The light emitting element can use the semiconductor light emittingelement, such as a LED (light emitting diode) element. The lightemitting element may be an element including an element structureconfigured of various semiconductors and provided with a pair ofpositive and negative electrodes. In particular, the light emittingelement preferably includes a nitride semiconductor(In_(x)Al_(y)Ga_(1-x-y)N, 0≦x, 0≦y, x+y≦1) that can effectively excitethe phosphor. In addition, the light emitting element maybe a galliumarsenide semiconductor element, or a gallium phosphide semiconductorelement. The light emitting element with a pair of positive and negativeelectrodes provided on the same surface side is face-up mounted byconnecting the respective electrodes to the conductive member via wires,or face-down (flip-chip) mounted by connecting the respective electrodesto the conductive member by a conductive adhesive. In a light emittingelement having a pair of positive and negative electrodes respectivelyon opposed surfaces thereof, a lower surface electrode is bonded to theconductive member by the conductive adhesive, and an upper surfaceelectrode is connected to the conductive member by the wires. The numberof light emitting elements mounted on one light emitting device may beone or plural. The light emitting elements can be connected in series orin parallel.

(Sealing Member 30)

The sealing member is a member for sealing the light emitting element.The base material of the sealing member has the electric insulation, andcan transmit light emitted from the light emitting element (preferably,transmittance of 70% or more). The base material before solidificationhad better be material having fluidity. Specifically, suitable materialsfor the base material of the sealing member can include a siliconeresin, an epoxy resin, a phenol resin, a polycarbonate resin, an acrylicresin, a TPX resin, a polynorbornene resin, a modified resin thereof ora hybrid resin thereof, and the like. Among them, the silicone resin ora modified resin thereof is preferably because of having excellentresistance to heat and light and a little volume contraction aftersolidification of the resin. The sealing member preferably contains afiller, phosphor, and the like in the base material, but does not needto contain them.

(Filler)

The filler for use can be made of a diffusing agent, coloring agent, orthe like. Specifically, suitable materials for the filler can includesilica, titanium oxide, magnesium oxide, magnesium carbonate, magnesiumhydroxide, calcium carbonate, calcium hydroxide, calcium silicate, zincoxide, barium titanate, aluminum oxide, iron oxide, chrome oxide,manganese oxide, glass, carbon black, and the like. The shapes of thefiller can include, for example, a spherical shape, an irregular crushedshape, a needle-like shape, a columnar shape, a plate-like shape(including a scale-like shape), a fiber-like shape, a dendritic shape,and the like (the same goes for the phosphor to be mentioned later) Thefiller may be made of hollow or porous material.

(Phosphor 50)

The phosphor absorbs at least a part of a primary light emitted from thelight emitting element and then outputs a secondary light with awavelength different from that of the primary light. Specifically, thephosphors can include an yttrium-aluminum-garnet activated by cerium, anitrogen-containing calcium aluminosilicate activated by europium and/orchromium, a sialon activated by europium, a silicate activated byeuropium, a potassium fluosilicate activated by manganese, or the like.Thus, the light emitting device can be one that emits primary andsecondary lights with visible wavelengths in a mixed color (for example,a white color), or one that emits a secondary light with a visiblewavelength which is excited by a primary ultraviolet light.

(Wire)

The wire is a member for electrically connecting the electrodes of thelight emitting element to the conductive members. Specifically, the wirefor use can be a metal wire made of gold, copper, silver, platinum,aluminum, or an alloy thereof. In particular, a gold wire is preferablebecause the gold wire is less likely to be broken due to stress from thesealing member and has excellent heat resistance or the like. In orderto obtain the high light extraction efficiency, the wire may have atleast its surface coated with silver.

(Adhesive)

An adhesive is a member for bonding the light emitting element to thebase substrate. The insulating adhesives for use can include, epoxyresin, silicone resin, polyimide resin, or a modified resin thereof or ahybrid resin thereof, or the like. The conductive adhesive for use caninclude a conductive paste, such as silver, gold or palladium, a solder,such as a gold-tin based solder, or a wax made of a low-melting pointmetal or the like.

EXAMPLES

Examples according to the present invention will be described in detailbelow. It is apparent that the present invention is not limited to thefollowing Examples.

EXAMPLE 1

A light emitting device of Example 1 is a top-view type SMD(surface-mount-device) LED that has the structure of the light emittingdevice 100 shown in FIGS. 1A and 1B.

The base substrate had a rectangular parallelepiped having dimensions of3.0 mm in length, 3.0 mm in width, and 0.52 mm in thickness. The basesubstrate was formed as a package made up of the molded body integrallyformed with apair of (first and second) positive and negative leadelectrodes. The base substrate was manufactured by setting a processedmetal plate (lead frame) with a plurality of sets of lead electrodesconnected in the longitudinal and lateral directions via suspensionleads in a die, injecting a liquid material for the molded body into thedie, solidifying the material, followed by removal of the die, and thencutting (singulating) the base substrate. In this example, the cuttingof the base substrate was performed after a sealing step of the lightemitting element.

Each of the first and second lead electrodes was a plate-like smallpiece having a maximum thickness of 0.2 mm, made of a copper alloy, andhaving its surface coated with silver coating. Exposed regions of thelower surface of the first and second lead electrodes were substantiallycoplanar with the lower surface of the molded body, thereby forming thelower surface of the base substrate. Each of the first and second leadelectrodes had a part of an end surface of the base substrate (cutsuspension lead portion) exposed. The exposed part had pits serving as acasterllation.

The molded body had a square appearance with 3.0 mm length, and 3.0 mmwidth as viewed from the upper side, and 0.52 mm in maximum thickness.The molded body was made of epoxy resin containing titanium oxide. Arecessed portion having a circular shape as viewed from the upper sidewas formed on the upper surface of the molded body, specifically,substantially at the center of the upper surface of the base substrate.The recessed portion had a diameter of 2.48 mm, and a depth of 0.32 mm.An inclination angle of the sidewall surface of the recessed portion was95° with respect to the bottom surface of the recessed portion.

The upper surface of each of the first and second lead electrodesconstituted a part of the bottom surface of the recessed portion. Thetwo light emitting elements were bonded to the upper surface of thefirst lead electrode with an adhesive made of silicone resin. Each ofthe two light emitting elements was a LED element including a laminateof nitride semiconductor element structures stacked on a sapphiresubstrate, and had the dimensions of 350 μm in length, 550 μm in widthand 120 μm in thickness. Each light emitting element can emit blue light(with a center wavelength of about 460 nm). In each of the two lightemitting elements, one of p and n electrodes was connected to the uppersurface of the first lead electrode via a wire, and the other of the pand n electrodes was connected to the upper surface of the second leadelectrode via a wire. The wire was a gold wire having a diameter of 25μm.

A protection element which was a Zener diode having an opposed electrodestructure with 150 μm in length, 150 μm in width and 85 μm in thicknesswas bonded to the upper surface of the second lead electrode with aconductive adhesive made of a silver paste. The protective element hadits upper surface electrode connected to the upper surface of the firstlead electrode via a wire.

The recessed portion of the base substrate was filled with the sealingmember to cover the light emitting elements. The sealing membercontained a phenyl silicone resin as a base material, a phosphor ofYttrium aluminum garnet (YAG:Ce) excited by cerium in the base material,and a filler (having 6 μm in diameter) made of silica, and particles ofzirconium oxide. The particle of the zirconium oxide had a particlediameter of about 5 nm, and undergoes a surface treatment of a siloxanecompound. The particles were blended in 0.2% by weight into the resin ofthe base material. The upper surface of the sealing member wassubstantially coplanar with the upper surface of the base substrate, andspecifically, had a substantially flat surface (strictly speaking, witha slight recessed surface due to hardening and contraction). The sealingmember was formed by putting the liquid material into the recessedportion of the base substrate by use of a dispenser or the like, andheating and solidifying the material. The phosphors were unevenlydistributed on the bottom side of the recessed portion.

FIG. 5 shows images of the top surface of an edge portion of the sealingmember observed by a scanning electron microscope (S-4800 manufacturedby Hitachi, Ltd.) in the light emitting device of Example 1. FIG. 6 isdata on the result of an energy dispersive X-ray (EDX) analysis of theedge portion of the sealing member shown in FIG. 5. FIG. 7 is an imageof a section of the edge portion of the sealing member shown in FIG. 5and observed by the scanning electron microscope. As can be seen fromFIGS. 5 and 6, at least a part of the edge portion of the sealing memberis located in the vicinity of the edge of the recessed portion of thebase substrate, and is a region where at least one of the particles ofzirconium oxide and aggregates of the particles are unevenlydistributed. This can also be confirmed in FIG. 7 (particularly, in apart indicated by an arrow).

The light emitting device of Example 1 with the above-mentionedstructure can exhibit the same effects as those of the light emittingdevice 100 of the first embodiment.

The light emitting device according to the present invention can beapplied to a backlight source of a liquid crystal display; variousillumination tools; a large-sized display; various types of displaydevices dedicated for advertisement, destination guidance, and the like;image readers, such as a digital video camera, a fax machine, a copymachine, and a scanner; a projector, and the like.

EXPLANATION OF REFERENCES IN DRAWINGS

-   10 Base substrate (11 . . . Upper surface, 15 . . . Recessed    portion, 17 Edge)-   20 Light emitting element-   30 Sealing member-   35 Base material of sealing member-   40 Surface-treated particle, or particle coexisting with dispersing    agent-   41 Aggregate of surface-treated particles, or aggregate of particles    coexisting with dispersing agent-   50 Phosphor-   60 Coating-   100, 200 Light emitting device

What is claimed is:
 1. A light emitting device, comprising: a base substrate having a recessed portion at an upper surface thereof; a light emitting element provided in the recessed portion; and a sealing member provided in the recessed portion, wherein the sealing member contains surface-treated particles, or particles coexisting with a dispersing agent, and at least a part of an edge portion of the sealing member is a region located in the vicinity of an edge of the recessed portion, at least one of the particles and aggregates of particles being unevenly distributed in the region.
 2. The light emitting device according to claim 1, wherein the particle is a nanoparticle.
 3. The light emitting device according to claim 1, wherein a content of the particles and/or the aggregates of the particles is in a range of 0.05% by weight or more and 50% by weight or less.
 4. The light emitting device according to claim 1, wherein a content of the particles and/or the aggregates of the particles is in a range of 0.1% by weight or more and 20% by weight or less.
 5. The light emitting device according to claim 1, wherein at least one of the particles or the aggregates of the particles exist at an outer edge of the sealing member.
 6. The light emitting device according to claim 1, wherein an end surface of the base substrate is a cut surface.
 7. The light emitting device according to claim 6, wherein a base material of the sealing member is made of silicone resin, modified silicone resin, silicon-modified resin or hybrid silicone resin.
 8. The light emitting device according to claim 1, wherein an upper surface of the sealing member is a surface extending upward in a convex shape.
 9. The light emitting device according to claim 1, wherein an inorganic coating is formed over an upper surface of the base substrate.
 10. The light emitting device according to claim 1, wherein a base material of the sealing member is phenyl silicone resin, and the particles are made of zirconium oxide.
 11. The light emitting device according to claim 1, wherein half or more the edge portion of the sealing member is the region located in the vicinity of the edge of the recessed portion, at least either one of the particles and aggregates of particles being unevenly distributed in the region.
 12. The light emitting device according to claim 1, wherein the particle has a spherical shape.
 13. The light emitting device according to claim 1, wherein the particle is an inorganic material.
 14. The light emitting device according to claim 1, wherein the particle is an organic material.
 15. The light emitting device according to claim 2, wherein the sealing member contains phosphors.
 16. The light emitting device according to claim 15, wherein the phosphors are at least on selected from the group consisting of yttrium-aluminum-garnet activated by cerium, a nitrogen-containing calcium aluminosilicate activated by europium and/or chromium, a sialon activated by europium, a silicate activated by europium, and a potassium fluosilicate activated by manganese.
 17. The light emitting device according to claim 2, wherein an end surface of the base substrate is a cut surface.
 18. The light emitting device according to claim 17, wherein a base material of the sealing member is made of silicone resin, modified silicone resin, silicon-modified resin or hybrid silicone resin.
 19. The light emitting device according to claim 18, wherein a base material of the sealing member is phenyl silicone resin, and the particles are made of zirconium oxide.
 20. The light emitting device according to claim 19, wherein a content of the particles and/or the aggregates of the particles is in a range of 0.1% by weight or more and 20% by weight or less. 